It is troublesome to draw ellipses and the precision of such ellipses drawn is very low. The most common method of drawing ellipses is to determine points by distances from the center and to connect the points into elliptic outline. Although it is broadly used, it takes time and effort and is apt to have errors. Conventional elliptical compasses can draw standard ellipses but can not be used broadly because the number of ellipses they can draw is limited. There are many ellipsographs currently available but they can only draw one size of ellipse and can not be used for a special purpose.
Aimed at the above mentioned disadvantages, the inventor worked hard to make improvements and after many experiments, developed this improved ellipsograph which employs a motor to cause circumferential, and linear movements at the same time for drawing ellipses.
The improved ellipsograph of this invention comprises a base frame, a slide block fitted into sliding grooves formed in the inside of the frame and capable of sliding back and forth freely. A worm wheel and a disc each relieved longitudinally to receive a movable block, are superimposed upon each other, screwed together and fitted in the round opening of the slide block. A small motor with a screw shaft is mounted on one side of the slide block with the shaft in mesh with the worm wheel. A pivot block and a stub attached thereto are mounted adjacent to each other on the worm wheel and on the disc so as to be slidable therein, and a drawing arm fixed to the pivot. When the motoris started, it will cause the worm wheel to turn and the pivot will circumambulate with the worm wheel. At the same time, the stub, fitted into a stub slot formed in the base of the frame, will roll along the slot and the tangential force of the worm wheel will force the slide block to move back and forth. The synchronous combination of circumferential and linear movements of the pivot will cause the drawing arm to draw ellipses, ovoids, circles, etc., as determined by the position of the pivot block and stub block.
The pivot and the stub are adjustable and made as an integral part respectively of the pivot adjusting block and the stub adjusting block. The pivot adjusting block and the stub adjusting block are fitted respectively in the worm wheel and the disc and have a threaded hole each for a screw rod to adjust their positions so that the drawing arm will draw ellipses of different sizes. Besides, a positioning plate, fitted on the base frame, can be pulled out for positioning so that the drawing arm will draw ellipses in the preset place. The drawing arm can be extended for drawing larger proportional ellipses. This improved ellipsograph is simple in structure but can draw ellipses, ovoids, and circles of different sizes.
The main object of this invention is to provide an improved ellipsograph which is simple in structure, low in cost and readily draws standard ellipses in preset places.
Another object of this invention is to provide an improved ellipsograph which can be adjusted to draw a variety of ellipses, ovoids and circles of different sizes.